Dental alloy for porcelain-fused-to-metal restorations

ABSTRACT

A dental alloy comprises 50-55% by weight gold, 10-20% by weight platinum, 0-10% by weight silver, 15-35% by weight nickel, 0-10% by weight indium, 0-10% by weight tin; and 0.1% by weight grain refiner. The dental alloy may be made by mixing preselected quantities of gold, platinum, nickel and a grain refiner, subjecting the mixture to a heating process until all the metals are brought to a molten state, and thereafter allowing the metals in the molten state to cool and cure in a mold.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 60/219,143 filed Jul. 17, 2000, the contents whereof are incorporated herein by reference in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

[0002] This invention relates to alloys and methods of manufacture thereof, and more particularly to an alloy comprising a number of metals which has a dental application and may be useful in dental restorations. The dental alloy of the invention is one which facilitates and enhances fusion between the metals comprising the alloy, and a porcelain covering for the dental alloy.

[0003] Alloys, and particularly alloys including a substantial proportion by weight of gold, have been used for many years in the preparation of dental restorations. The alloys may typically comprise a plurality metals, ingredients and compositions, which, when appropriately combined, result in the formation of a dental alloy which may be well suited for such applications as dental caps, bridges and crowns. Typically, the dental restoration comprises a dental alloy which may constitute a substructure which is very hard and seals the tooth from external substances that may result in decay, and a porcelain veneer material covering all or a part of the dental alloy for cosmetic purposes. The relationship between the dental alloy and the porcelain material is such that they are fused together, thereby providing a permanent restoration to dental wear and fractures which may result from broken or decayed teeth.

[0004] One of the difficulties typically encountered in the use of conventional dental alloys arises largely from the fact that metal alloys are not supplied in an affordable alloy form in a high noble material category. Such a metal alloy should not only be suitable for sealing the exterior exposed surface portion of a tooth, but should also readily fuse with the porcelain material is or veneer which is applied to the metal alloy as a coating or jacket, and has desirable properties and characteristics from a cosmetic perspective.

[0005] Therefore, there is a need to provide a metal dental alloy for use in dental applications, where the alloy will readily seal the exterior surfaces of a tooth, and which will also fuse to porcelain, so as to thereby provide a permanent restoration of the tooth, as well as a superior cosmetic appearance. Preferably, metals high on the list of noble materials would be used, and the resulting metal alloy should be both easy and economical to manufacture and use.

SUMMARY OF THE INVENTION

[0006] According to one aspect of the invention, there is provided an alloy for dental applications comprising gold, platinum, nickel and a grain refiner. Preferably, the gold comprises 50-60% by weight of the alloy, and most preferably 55% by weight of the alloy. Preferably, the platinum comprises 5-20% by weight of the alloy, more preferably 10-20% by weight of the alloy, and most preferably 10% by weight of the alloy.

[0007] Preferably, the nickel comprises 15-35% by weight of the alloy, more preferably 20-30% by weight of the alloy, and most preferably 25% by weight of the alloy.

[0008] The alloy may further comprise silver, preferably in the amount of 1-20% by weight of the alloy, more preferably 10% by weight of the alloy. The alloy may further comprise indium, preferably in the amount of 1-20% by weight of the alloy, more preferably 0.5% by weight of the alloy. The alloy may further comprise tin, preferably in the amount of 1-10% by weight of the alloy, more preferably 0.25% by weight of the alloy.

[0009] Preferably, the grain refiner comprises a mixture of ruthenium, iridium and rhenium, which may be present in substantially equal quantities. The grain refiner may constitute 0.1% by weight of the alloy.

[0010] In one specific aspect, the invention is for an alloy comprising 50-55% by weight gold, 10-20% by weight platinum, 0-10% by weight silver, 15-35% by weight nickel, 0-10% by weight indium, 0-10% by weight tin, and 0.1% by weight grain refiner. Preferably, the alloy comprises 55% by weight gold, 10% by weight platinum, 10% by weight silver, 25% by weight nickel, 0.5% by weight indium, 0.25% by weight tin, and 0.1% by weight of grain refiner.

[0011] According to another aspect of the invention, there is provided a method of making an alloy comprising the steps of mixing preselected quantities of gold, platinum, nickel and a grain refiner, subjecting the mixture to a heating process until all the metals are brought to a molten state, and thereafter allowing the metals in the molten state to cool and cure in a mold.

[0012] Preferably, the metals are mixed in a crucible and in a protective environment comprising a substantially noble gas.

[0013] Accordingly, one aspect of the invention provides a composition and method which ma y avoid the problem s and difficulties of the prior art, by providing a dental alloy which is suitable for porcelain-to-metal restoration, and which may be readily fused together with the porcelain to provide an integral and unitary construction.

[0014] The dental alloy of the invention may include a combination of metals selected from the group consisting of gold, platinum, silver, nickel, indium, tin, as well as a mixture of a grain refiner. The preferred proportion of each of the metals contained within the dental alloy of the invention comprises one where gold represents at least 50% of the formulation, with the remainder of the metals preferably decreasing in percentage to tin, silver and indium, which may represent as much as 10%, by weight, of the dental alloy, or indeed be completely eliminated from the alloy.

[0015] All of the metal ingredients are analytically weighted to formulation and, in preparation, are layered, preferably in a crucible, with the lighter trace metals located at or near the bottom of the crucible. Once the metals have been layered within the crucible, they are all brought to a molten state, preferably in a protective environment, such as one consisting of an inert or noble gas, and thereafter poured into a mold for curing.

[0016] In one aspect, an important component of the present invention provides an alloy for use in dental applications, for the purposes of reconstructing and/or restoring dental elements including teeth, bridges, caps and the like, with the invention using porcelain-fused-to-metal construction techniques.

[0017] In another aspect, the present invention relates to providing a particular formulation of a metal alloy comprising a number of components of preferred percentage content by weight, so that an improved dental alloy is produced which is suitable for sealing exposed surfaces on a tooth, and which will also accept, for fusion, the application of porcelain thereto, wherein the porcelain is applied primarily for cosmetic purposes.

[0018] In yet a further aspect, the present invention provides a metal alloy which is affordable to produce, and used for dental restorations which may be supplied in a high noble category.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0019] In accordance with one aspect of the present invention, a dental alloy for porcelain-fused-to-metal restoration is provided, and comprises, in various proportions by weight, gold, platinum, nickel, and grain refiner. The grain refiner may be a combination of compounds such as ruthenium, iridium and rhenium. Preferably, the dental alloy of the invention may further comprise silver, indium and tin.

[0020] In one form, the dental alloy of the invention is comprised of the following compounds in the amounts indicated: COMPOUND PERCENTAGE RANGE BY WEIGHT Gold 50-55% Platinum 10-20% Silver  0-10% Nickel 15-35% Indium  0-10% Tin  0-10% Grain Refiner 0.1-0.3%

[0021] In the embodiment set forth above, the grain refiner comprises a mixture of ruthenium, iridium and rhenium.

[0022] In a preferred embodiment of the invention, the dental alloy is comprised as follows: COMPOUND PERCENTAGE RANGE BY WEIGHT Gold 55% Platinum 10% Silver 10% Nickel 25% Indium 0.5%  Tin 0.25%   Mixture of Ruthenium, 0.1%  Iridium and Rhenium

[0023] The metal alloy for dental applications is prepared by weighing each ingredient to a specific formulation so as to provide a specific amount by weight for each ingredient as a percentage or a proportion of the total weight. When each ingredient has been so weighed out and prepared, the various metals comprising the dental alloy are layered in a crucible. Preferably, the lighter trace metals (such as ruthenium, iridium and/or rhenium) are located at the bottom of the crucible. Once all the different metals which comprise the dental alloy under preparation have been laid on top of the lighter trace metals, the crucible is then heated to a temperature whereby all of the metals are brought into a molten state.

[0024] In one example for layering the metals and heating them to a molten state, the bottom layer is comprised of the trace minerals, with the next layer above it being comprised of the metal constituting the highest percentage by weight of the alloy, followed by layers of metals having a decreasing percentage by weight of the total alloy weight. In the preferred example set forth above, the metal having the greatest percentage by weight of the alloy, which is gold, is on top of the base layer of trace metals, and the metal(s) having the least or lowest percentage by weight, such as indium and tin, will be the furthest from the trace mineral bottom layer. In this condition, sufficient heat is applied to the crucible to bring the various metals to a temperature where each of the metals reaches a liquid or molten state. Normally, this condition can be visually observed. Preferably, the metals are located and heated within an inert gas protective environment for the molten metal. Such an inert or noble gas may be comprised of neon, argon or the like.

[0025] Once the metals are in a molten state, the alloy so produced by the metals is poured from the crucible into a mold where it is allowed to cool and cure.

[0026] While preferred embodiments of the present invention have been shown and described above, both with respect to metal content and the respective percentage ranges by weight of each of these metals, it will be apparent to those skilled in the art that variations and modifications may be made, within the scope of this invention. 

1. An alloy for dental applications comprising gold, platinum, nickel and a grain refiner.
 2. An alloy as claimed in claim 1 wherein the gold comprises 50-60% by weight of the alloy.
 3. An alloy as claimed in claim 2 wherein the gold comprises 55% by weight of the alloy.
 4. An alloy as claimed in claim 1 wherein the platinum comprises 5-20% by weight of the alloy.
 5. An alloy as claimed in claim 4 wherein the platinum comprises 10-20% by weight of the alloy.
 6. An alloy as claimed in claim 4 wherein the platinum comprises 10% by weight of the alloy.
 7. An alloy as claimed in claim 1 wherein the nickel comprises 15-35% by weight of the alloy.
 8. An alloy as claimed in claim 7 wherein the nickel comprises 20-30% by weight of the alloy.
 9. An alloy as claimed in claim 7 wherein the nickel comprises 25% by weight of the alloy.
 10. An alloy as claimed in claim 1 further comprising silver.
 11. An alloy as claimed in claim 10 wherein the silver constitutes 1-20% by weight of the alloy.
 12. An alloy as claimed in claim 10 wherein the silver comprises 10% by weight of the alloy.
 13. An alloy as claimed in claim 1 further comprising indium.
 14. An alloy as claimed in claim 13 wherein the indium comprises 1-20% by weight of the alloy.
 15. An alloy as claimed in claim 13 wherein the indium comprises 0.5% by weight of the alloy.
 16. An alloy as claimed in claim 1 further comprising tin.
 17. An alloy as claimed in claim 16 wherein the tin comprises 1-10% by weight of the alloy.
 18. An alloy as claimed in claim 16 wherein the tin comprises 0.25% by weight of the alloy.
 19. An alloy as claimed in claim 1 wherein the grain refiner comprises a mixture of ruthenium, iridium and rhenium.
 20. An alloy as claimed in claim 19 wherein the ruthenium, iridium and rhenium are present in substantially equal quantities.
 21. An alloy as claimed in claim 1 wherein the grain refiner constitutes 0.1% by weight of the alloy.
 22. A method of making an alloy comprising the steps of mixing preselected quantities of gold, platinum, nickel and a grain refiner, subjecting the mixture to a heating process until all the metals are brought to a molten state, and thereafter allowing the metals in the molten state to cool and cure in a mold.
 23. A method as claimed in claim 22 wherein the metals are mixed in a crucible.
 24. A method as claimed in claim 23 wherein the grain refiner forms a lowermost first layer within the crucible, the metal having the greatest constituent by weight of the metal alloy forms a second layer, with subsequent layers being formed respectively by metals having a sequentially decreasing constituent proportion by weight in the metal alloy.
 25. A method as claimed in claim 22 when carried out in a protective environment comprising a substantially noble gas.
 26. An alloy comprising 50-55% by weight gold, 10-20% by weight platinum, 0-10% by weight silver, 15-35% by weight nickel, 0-10% by weight indium, 0-10% by weight tin; and 0.1% by weight grain refiner.
 27. An alloy as claimed in claim 26 comprising 55% by weight gold, 10% by weight platinum, 10% by weight silver, 25% by weight nickel, 0.5% by weight indium, 0.25% by weight tin, and 0.1% by weight of grain refiner. [The total percentages in claim 27 slightly exceed 100%. Please reconfigure so that total percentage adds up to 100%].
 28. An alloy as claimed in claim 26, wherein the grain refiner comprises a mixture of ruthenium, iridium and rhenium. 